1. Field of the Invention
The present invention relates to a webbing take-up device that configures a seat belt for restraining, with a long band-like webbing belt, the body of a vehicle occupant seated in a seat of a vehicle.
2. Description of the Related Art
Seat belt devices that restrain, with a long band-like webbing belt, the body of a vehicle occupant seated in a seat of a vehicle, are disposed with a webbing take-up device fixed to the vehicle body at the side of the seat. The webbing take-up device is disposed with a spool (take-up shaft) whose axial direction is along the substantial front-rear direction of the vehicle, for example. A longitudinal-direction base end side of the webbing belt is attached to the spool.
The webbing belt is taken up and accommodated on the spool from the longitudinal-direction base end side of the webbing belt. When the webbing belt is placed around the body of the vehicle occupant, the webbing belt is pulled towards the leading end side, and the webbing belt accommodated in the taken-up state on the spool is pulled out.
Next, the pulled-out webbing belt is placed around the body of the vehicle occupant. Then, a tongue plate disposed at a longitudinal-direction intermediate portion of the webbing belt is inserted into a buckle device disposed opposite from the webbing take-up device via the seat.
Thus, the tongue plate is retained in the buckle device, and the state in which the webbing belt is placed around the body of the vehicle occupant is retained.
A spiral spring is directly or indirectly coupled to one axial-direction end of the spool. When the webbing belt taken up on the spool is pulled out as described above, the spool rotates in a pullout direction, which is one direction around its axis. When the spool rotates in the pullout direction in this manner, the spiral spring is tightened and urges the spool in the take-up direction.
In the state where the webbing belt is placed around the body of the vehicle occupant, the urging force of the spiral spring causes the slack part of the webbing belt to be taken up on the spool, and causes the webbing belt to be fitted to the body of the vehicle occupant. Then, when the tongue plate is removed from the buckle device, the urging force of the spiral spring causes the spool to rotate in the take-up direction opposite from the pullout direction, and causes the webbing belt to be taken up and accommodated on the spool.
There is also a webbing take-up device having a configuration where the spool is caused to rotate in the take-up direction by the drive force of a motor. An example thereof is disclosed in Japanese Patent Application Laid-Open Publication (JP-A) No. 11-227567.
In the webbing take-up device disclosed in JP-A No. 11-227567, control device for driving/controlling the motor is connected to detecting means (called a “buckle connection detector” in the above publication) such as a buckle switch disposed in the buckle device. When the detecting means detects that the tongue plate has been removed from the buckle device, the control device drives the motor.
In the configuration where the webbing belt is taken up by the drive force of a motor in this manner, the spiral spring becomes unnecessary, or, if a spiral spring is concomitantly used, the spring constant of the spiral spring can be reduced. Because the urging force of the spiral spring increases as the spiral spring is tightened, there is also the potential for the tension of the webbing belt corresponding to the urging force of the spiral spring to impart a feeling of tightness to the vehicle occupant when the webbing belt is placed around the body of the vehicle occupant.
In the configuration where the webbing belt is taken up by the drive force of a motor as described above, the feeling of tightness that the vehicle occupant experiences when the webbing belt is placed around the body of the vehicle occupant can be eliminated or reduced by eliminating the spiral spring or reducing the spring constant of the spiral spring.
Incidentally, in the case of the configuration where the spool is rotated in the take-up direction by the drive force of a motor and the webbing belt is taken up and accommodated on the spool in this manner, the necessary take-up time is set as the drive time of the motor necessary until the entire webbing belt is accommodated from the state in which the entire webbing belt has been pulled out, and after the tongue plate is removed from the buckle device as described above, the control device of the motor drives the motor only for the necessary take-up time.
Here, for example, in a state where the webbing belt is removed from the body of the vehicle occupant, sometimes the tongue plate and/or part of the webbing belt becomes caught between the door panel and the peripheral edge of the door opening that the door panel opens and closes, or else the webbing belt catches on part of the seat, so that it becomes impossible for the webbing belt to be taken up by only the rotational force of the spool in the take-up direction.
However, the motor continues to be driven even when it is impossible for the webbing belt to be taken up. Thus, even if the vehicle occupant were to become aware of the fact that it is impossible for the webbing belt to be taken up and eliminate this problem, the motor ends up being stopped when the necessary take-up time elapses after the start of the driving of the motor. For this reason, the webbing belt is not completely accommodated on the spool (so-called “totally accommodated state”), and its appearance is poor.